Study: Carbon Dioxide Directly Increases Allergy-Causing Pollen
By By Umair Irfan, E&E reporter
November 10, 2014, 4:22:45 AM EST
The annual surge of sneezing, watery eyes and runny noses for allergy sufferers is only poised to get worse as the climate changes, and new research shows that greenhouse gases have a direct effect on aggravating these problems.
Warmer winters and precipitation changes are already creating longer and more severe allergy seasons in parts of the world, resulting in a multibillion-dollar price tag from treatment and lost productivity (ClimateWire, Nov. 29, 2012).
But it's not just the temperature that's raising pollen counts from trees and grasses; carbon dioxide and ozone have an immediate and direct impact on pollen, according to a recent report published in the journal PLOS ONE.
Christine Rogers, a co-author and research assistant professor in the School of Public Health and Health Sciences at the University of Massachusetts, Amherst, said her team investigated Timothy grass, Phleum pratense.
"It's important to look at grasses because grasses are found in biomes all over the world, and grass pollen allergies are found all over the world," she explained.
The research team measured pollen counts from the grass in a laboratory, comparing the amount produced under higher concentrations of carbon dioxide, up to 800 parts per million, and ozone up to 80 parts per billion. The concentrations reflect greenhouse gas projections to the year 2100.
Researchers found that carbon dioxide tends to increase pollen production in plants while ozone tends to decrease production. However, when they combined the two gases, higher carbon dioxide concentrations raised pollen production by 50 percent, regardless of how much ozone was present. Based on these findings, the researchers also projected that grass pollen concentrations could increase by 200 percent under a climate change scenario.
Overlapping pollen seasons
Grass pollen tends to rise during summers, while tree pollen peaks in the spring and ragweed in the fall. As growing seasons get longer, different allergens are more likely to overlap, creating more problems for people with allergies.
Rogers and her collaborators also found that under high carbon dioxide concentrations, the pollen itself becomes more likely to trigger an allergic reaction. "On the surface of the pollen are a number of proteins that we can become allergic to," she said. "That number of allergenic proteins can vary."
The researchers cautioned that their projections were preliminary and that they still need to test how greenhouse gases alter pollen levels in the real world. "It was a chamber study with plants in a pot," explained co-author Jennifer Albertine, a postdoctoral researcher in the environmental conservation department at the University of Massachusetts, Amherst. "There are limitations to how much you can extrapolate."
"The idea that you're going to see a linear response between climate change allergens is a risky proposition in any case," said Lewis Ziska, a plant physiologist at the Department of Agriculture's Agricultural Research Service, who was not involved in this study. He explained that changes in the climate could create tipping points that will push pollen in the other direction, such as temperatures that get too hot for grasses to prosper or rainfall patterns that make ragweed plants put down roots in new habitats.
However, much of the research on how greenhouse gases influence pollen focuses on the climate and not on the gases themselves. "This is one of the really insightful papers that I've seen come along that addresses this aspect," he said. Allergy costs outweigh crop benefits
Though some groups have argued that carbon dioxide is plant food and will therefore be a net positive for humanity from increased crop yields, Ziska said increasing allergen production would likely outweigh any benefits from more wheat or rice.
The study also demonstrates that the impact of greenhouse gases on allergy sufferers can change depending on the gas. "What I liked about this [paper] is that they showed the negative effects" of ozone, said Leonard Bielory, an attending physician and allergist at the Robert Wood Johnson University Hospital and a professor at Rutgers University's Center for Environmental Prediction. "What it teaches me is nothing is one-dimensional."
Bielory, who was not involved in this research, added that allergy risk is a convergence of many factors, including how sensitized people are to allergens, temperature, seasonal variation, urban development, plant genetics and epigenetic factors that act outside of a plant's genome, like greenhouse gases. The number of people sensitized to pollen has doubled in the past 20 years, and many people are allergic to more than one variety.
Even ambient carbon dioxide from vehicle traffic can increase pollen concentrations in an area, so Bielory suggested health officials should recognize that allergy risk is highly localized and should tailor their projections accordingly.
Albertine and Rogers said they are now investigating how greenhouse gases affect other pollen producers. They also want to study how immediate effects from greenhouse gases intersect with long-term warming trends when it comes to allergies.
Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.E&E Publishing is the leading source for comprehensive, daily coverage of environmental and energy issues. Click here to start a free trial to E&E's information services.
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